The disclosure of Japanese Patent Application No. 2000-035157 filed on Feb. 14, 2000 including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a vehicular brake control apparatus and a vehicular brake control method that limits braking forces applied to rear wheels of a vehicle in comparison with those applied to front wheels of the vehicle.
2. Description of Related Art
There is known a brake control apparatus that limits braking forces distributed to rear wheels to prevent the rear wheels from being locked during a braking operation at a high speed. According to Japanese Patent Application Laid-Open No. 5-213169, if the deceleration has become equal to or higher than a predetermined value at the time of braking, the fluid pressures for transmitting braking forces to rear wheels are maintained. This can prevent the rear wheels from being locked prior to the locking of front wheels, and effectively preclude the vehicle from slipping sideways at the time of braking.
However, according to the aforementioned apparatus, the braking forces applied to the rear wheels are limited once the predetermined deceleration is reached. Therefore, even if the driver has depressed a brake pedal in an attempt to increase braking forces, they do not increase. As a result, the driver feels a sense of incongruity during a braking operation.
It is an object of the invention to provide a vehicular brake control method that maintain braking performance and stability of the vehicle and do not cause a sense of incongruity to the driver during a braking operation.
A vehicular brake control apparatus according to a first aspect of the invention includes a brake controller that limits, if the vehicle is in a predetermined driving state, braking forces applied to rear wheels of the vehicle in comparison with braking forces applied to front wheels of the vehicle. The brake controller also determines a brake operating amount by a driver. The brake controller increases the braking forces applied to the rear wheels if the brake controllers determines during the braking force limiting that the brake operating amount has increased.
According to the first aspect of the invention, if the brake operating amount has increased, the braking forces applied to the rear wheels, as well as those applied to the front wheels, are increased, whereby the decelerating force acting on the vehicle is increased. This provides a vehicle behavior suited for the feeling of the driver.
The brake controller determines, if the deceleration of the vehicle is equal to or higher than a predetermined value, that the vehicle is in the predetermined driving state, and limits the braking forces applied to the rear wheels based on the deceleration, thereby preventing the locking of the wheels and stabilizing the behavior of the vehicle. As the braking force limiting is not performed if the deceleration is low, the braking performance is improved.
The brake controller may determine that the brake operating amount by the driver has increased, by determining that the deceleration of the vehicle has increased. If the driver has further depressed the brake pedal during the braking force limiting, the braking forces applied to the front wheels are not limited. Therefore, the braking forces applied to the front wheels increase in accordance with the operation of the pedal, so that the deceleration of the vehicle increases. Accordingly, the increased brake operating amount can also be determined from an increase in the deceleration of the vehicle.